Peripheral nerve and trunk blocks

1

Why would you perform a peripheral nerve block?

Nerve blocks are generally performed for two major indications: anesthesia or analgesia. An anesthetic peripheral nerve block may allow a patient to avoid general anesthesia and periprocedural pain medication. This can be very helpful for patients with risk factors, such as a difficult airway or intolerance to general anesthesia. Analgesic blocks are similar but do not have adequate density or coverage to enable avoidance of general anesthesia. The primary benefit to an analgesic block is to avoid postoperative opioids and their associated side effects, thus improving postoperative pain scores, increasing patient satisfaction, decreasing nausea, and decreasing the likelihood a patient requires postoperative admission for pain control.

2

Which patients are not good candidates for a peripheral nerve block?

Nerve blocks can be associated with postoperative nerve damage. It is important to minimize this risk by only offering blocks to patients that are low risk for this complication. The most common reason to avoid offering a patient a nerve block is anticoagulation. If a patient has an intrinsic or pharmacological coagulopathy, there is an increased risk of hematoma formation and subsequent nerve damage. The American Society of Regional Anesthesia antithrombotic therapy guidelines, updated in April 2018, are very helpful for deciding who is an appropriate candidate. Also a peripheral neuropathy, such as symptomatic spinal stenosis or Guillain-Barré, may increase the risk. Alternatively, a successful nerve block after a traumatic injury can mask diagnosis of a compartment syndrome, delaying critical treatment. Lastly, if a patient has a systemic infection, placement of a nerve catheter can result in a perineural abscess.

3

What are the most common nerve blocks of the upper extremity?

Most upper extremity nerve blocks involve blocking the brachial plexus at different anatomic locations. The blocks of the upper extremity are named for their anatomic correlation for probe position or needle insertion. Interscalene, supraclavicular, infraclavicular, and axillary are the most common brachial plexus blocks. With increased use of ultrasound, the supraclavicular block has become the mainstay for procedures below the shoulder. Individualized radial, median, and ulnar nerve blocks can be performed under ultrasound guidance to offer analgesia to the hand and fingers, while allowing for continued gross motor function.

4

How do you decide which brachial plexus block is most suitable for various procedures on the upper extremity?

The interscalene brachial plexus block is most suitable for procedures on the shoulder, distal clavicle, and proximal humerus. This is discussed separately in chapter 66 . Supraclavicular, infraclavicular, and axillary brachial plexus blocks are detailed in Table 69.1 .

5

What are the anatomic landmarks and basic technique for the supraclavicular, infraclavicular, and axillary brachial plexus blocks?

The supraclavicular nerve block is typically performed in the semi-sitting position, with the head turned to the opposite side. Reaching the arm to the ipsilateral lower extremity and externally rotating the shoulder helps depress the clavicle and increase space for the ultrasound probe. The needle is advanced from lateral to medial and local anesthetic is deposited, surrounding the divisions of the brachial plexus, lateral to the subclavian artery. Care must be taken to avoid any traversing arteries, as widespread variations in anatomy exist in the supraclavicular region.

The infraclavicular nerve block is a deep block that has the added benefits of avoiding phrenic nerve paralysis and accommodation of peripheral nerve catheters. The patient is positioned supine and the arm is positioned either at the patient’s side or above the head to elevate the clavicle and increase room for the ultrasound probe. The probe is oriented cephalad to caudad at the level of the coracoid process. The needle is advanced, until it is at approximately the 6 o’clock position of the axillary artery, and local anesthetic is deposited. This block provides coverage of all three cords of the brachial plexus with one injection. Note, it is important to achieve U shaped spread to both sides of the artery to avoid sparing of the medial or lateral cords.

The axillary nerve block is performed with the patient’s arm is abducted to approximately 90 degrees. The transducer is placed along the medial aspect of the arm in the axilla and the needle is traversed from cephalad to caudad to the 6 o’clock position of the axillary artery. Multiple injections are often required to achieve circumferential spread to anesthetize the median, ulnar, and radial nerves. A separate needle insertion point to anesthetize the musculocutaneous nerve is often required to ensure adequate distal forearm coverage.